This proposal is divided into three sections, each with a separate, specific objective. The first section of the proposal is entitled "The Surgical Treatment of Supraventricular Tachyarrhythmias" and is designed to expand and define the role of surgery in the treatment of certain types of supraventricular tachyarrhythmias, including ectopic (automatic) left atrial tachycardia, atrial flutter/fibrillation associated with mitral valve disease, AV node reentry tachycardia, and postoperative atrial flutter/fibrillation following elective cardioplegic arrest. The second section of the proposal is entitled "The Surgical Treatment of Ventricular Tachyarrhythmias" and is designed to determine the effectiveness and side-effects of new direct surgical techniques for the treatment of refractory ischemic ventricular tachycardia and to develop safe and effective surgical approaches to the treatment of ventricular tachyarrhythmias that are not associated with ischemic heart disease, particularly those originating in the right ventricle. The third section of the proposal is entitled "The Development of an Intraoperative and Postoperative Electrophysiologic Monitoring System" and is designed to establish a method by which myocardia integrity can be monitored on a continuous, real-time basis during and after cardiac surgical procedures.